Furnace system



R` D. MORROW FURNACE SYSTEM Filed May 12, 1960 July 16, 1963 Robert D.Mor-raw BY g I f d c ATTORNEYS United States Patent 3,097,686 FURNACESYSTEM Robert D. Morrow, Baltimore, Md., assignor to Product DevelopmentAssociates, Ltd., Baltimo'e, Md. Filed May 12, 1960, Ser. No. 28,588 14Claims. (Cl. 158-1) This invention relates to a furnace system forheating water or 'another suitable fluid medium and more particularly toa heating system wherein the hotter portions of the flue gases are fedback into the input of a combustion chamber.

Various systems are known wherein portions of the exhaust products orflue gases are fed back to the -input of a comb ustion chamber toimprove the overall efiiciency of a heating system. However, thesesystems suffer from the serious disadvantage in tha-t there is little-or no selectivity exercised with respect to which portions -of the fluegas are recrculated through the system. In most instances the feed backgases are selected on :a quantity basis with a certain percentagepassing through 'a ratio valve or other type of valving system so that acertain portion of the entire exhaust gas composition -is recirculatedto the combustion chamber.

The present invention provides a heating system having substantiallyincreased efiiciency which incorporates a selective feed back of fluegases from the exhaust system of -a combustion chamber to the inputwherein the fed back exhaust gases are mixed with fuel and air enteringthe combustion chamber. The selectivity is exercised through a vortextube which separates the exhaust gases into relatively warm and coldcomponents. The cold Component is permitted to exhaust to the atmosphereand only the warm component is fed back to the input of the heatingsystem. In this way it is possible to reduce the temperature of theexiting gases from the system and consequently substantially increasethe thermal eficiency of the furnace. It is theoretically possible byactually cooling the exhaust gases below atmospheric temperature toobtain a thermal efficiency for the' heating system of the presentinvention of over 100% It is therefore, a primary object of the presentinvention to provide a -novel heating system having increasedefficiency.

Another object of the present invention to provide a heating systemhaving sele'ctive feed back of portions of the flue gas exhaust to thesystem input.

Another object of the present invention is to provide a heating systemwith flue gas feed back and incorporating means for separating theexhaust gas into distinct components and feeding back only the hotterComponent to the system input.

These and other objeets and advantages of the invention will be moreapparent upon reference to the following specification, claims 'andappended drawings wherein:

FIGURE 1 is schematic diagram showing in simplified form the basicheating 'system of the invention and,

FIGURE 2 is a schematic diagram of a modified embodiment of the heatingsystem of the present invention.

Referring to the drawings and particularly to FIGURE l, the heatingsystem of the present invention generally indicated at comprises a gasinlet conduit 12 which -supplies either ambient or super charged air tothe input of an air blower 14. Fuel is supplied from any suitable sourceto the system through a supply pipe 16 connected to a restricted portion18 in the output line 20 of the blower which restricted portion definesa venturi connection so that the pressurized air flowing from outlet 20through the restriction 18 draws fuel from pipe 16. The pressurizedair-fuel mixture passes through -a check valve 22 in the direction ofthe arrow to :a combustion chamber .surrounding the cooler gas.

Patented July 16, 1963 ice 24 forming the major heating chamber of thefurnacc system.

Combusti-on products from chamber 24 pass outwardly in the direction ofthe arrow through a second check valve 26 to a conventional uniflowvortex tube 28. Vortex tube 28 is the type sometimes referred to as aRanque- Hilsch tube first described by G. Ranque in U.S. Patent1,952,28l. In the system illustrated the vortex tube is of the uniflowtype with the relatively hot and cold gas outlets positioned at the sameend of the tube.

It is well known that in operation a vortex tube divides a compressedgas into two moving streams each with a different temperature. The outerstream is substantially hotter than the inner one. The exact mode ofoperation is not fully understood and several theories have beenadvanced for explaining the operation of these tubes. One of the mostwidely accepted theories presumes that the gas is broken up intoseparate helical gyrating layers with the inner layer compressing theouter layer through centrifugal force and giving up some ot its energyto the outer layer. The energy given up is represented by an increase intemperature of the outer layer and a decrease in temperature of theinner layer each of which may be separately 'removed from the same endof a uniflow tube by means 'of suitably positioned and throttledconcentric apertures. It 'has been found that a maximum temperaturedifferential between the exiting relatively hot and cool gas streams isobtained by a division of 30% of cold gas and 70% hot gas. Temperaturedifferentials of as much as F. are not unusual.

As shown the vortex tube 28 comprises a generator chamber 30 and avortex generator 32 having a tangential inlet 34 through which the highpressure gases gain access to the central tubular channel 36 of thevortex tube. The gases are cause-d to spiral through the tube so thecooler portions of the gas collect in a central stream and the warmerportions collect in an outer iannular stream The central cooler streamis extracted through a central restriction 38 and passes to `atmospherethrough outlet conduit 40. Hotter portions of the flue gas passoutwardly through the outer re'striction 42 to a hot gas feed back line44.

Feed back line 44 Supplies the hotter portion of the exhaust or fluegases to the inlet conduit 12 where these hotter portions are mixed withthe incoming air supplied to a blower 14 and tend to preheat this air.In operation, the air-fuel mixture feed to the combustion chamber iscontrolled so that it contains approxim-ately 200% excess air. Thisexcess air serves to sustain complete combustion and further lowers thetemperature in the combustion chamber to an acceptable Value.

The combustion chamber and Vortex tube are surrounded by an insulatingjacket 46 containing a heat exchange fluid such `ras water as indicatedat 48 which takes heat produced in the combustion chamber from the outersurface of the vortex tube 36 and from the hot gas feed back line '44.Cold water may be supplied to the Water jacket through inlet 50 from asuitable supply and the hot water is drawn oli through 'outlet conduit52.

In operation, as the air fuel mixture burns in the com bustion chamberthe pressure in the chamber -rises` forcing the flue gases into thevortex generator of the vortex tube. Water is circulated over thechamber and tube extracting heat to be used for any suitable hot Waterheating system application such as tap water or for use in a hot watertype radiant heating system. The products of combustion are removed fromthe center :or colder section of the vortex tube through outlet conduit40. The excess air tends to be retained in the outer air stream of thevortex tube and is returned to the high pressure side lOf the combustionchamber.

FIGURE 2 shows a schematic diagram of a modified embodment of theheating system of the present invention with like elements bearing likereference numerals. In the system of FIGURE 2-the blower is eliminatedand in its place the combustion chamber -is fed by means of a novelinjecter and check valve arrangement. As in the embodiment of FIGURE 1,water to be heated is circulated through the jacket 46 from inletconduit 50 by suitable means such as the circulating pump 54 and isdrawn off through Conduit 52.

The hotter portion of the exhaust or flue gases is drawn off from theperiphery of the Hilsch tube and fed back through line 44. A portion ofthe combustion products is fed through pipe 58 from the combustionchamber 24 into a converging-diverging nozzle 60 where the combustionproducts attain supersonic velocities. The stream of high velocitycombustion products impinges on ambient air supplied by way of line 62and check valve 64 imparting velocity to the air molecules. The air andcombustion products enter a diffuser 66 where they are compressed to apressure higher than the pressure existing in the combustion chamber.This high pressure air and combustion mixture then picks up the fuel atthe throat of venturi 68 and enters the combustion chamber through line70 to sustain the steady flow combustion process. In so doing themixture passes through check valves 72 and 74.

The fuel is fed from a suitable source to line 75 and through a venturi76 where it picks up a small amount of ambient air from line 78. Thefuel and small quantity of ambient air enter the system at venturi 68between the two check valves 72 and 74. The air-fuel mixture supplied byway of venturi 68 into the combustion chamber is adequate during thestarting of the furnace. However, once the furnace is started the gasesflowing through the injecter comprising nozzle 60 'and diffuser 66 actsto pull more air from line 62. The increased pull of :air from line 62in turn acts to pull rnore fuel by way of Venturi 68 as it passesthrough the venturi between the check valves and the systemautomatically builds up to an Operating level. The check valve 64 in theair line serves only to prevent reverse flow in the event of amalfunction in the injecter.

It is apparent from the above that the present invention provides anovel heating system of substantially increased etficiency whichtheoretically may possess a thermal eiiiciency greater than 100% byactually cooling down the exhaust gases below ambient temperature. Animportant feature of the present invention is the selective feed back ofa hot component of exhaust gas to the combustion chamber inlet with theseparation of the exhaust gas into a hot component being accompanied bya separation of the remaining portion of the exhaust gas into a coldercomponent.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presenternbodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingndicated by the apperded claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be Secured by United States LettersPatent is:

1. A furnace system comprising a combustion chamber, means for supplyingfuel to said chamber, means forming an output path for combustionproducts from said chamber, means in said path for dividing thecombustion products into relatively hot and cold components and meansfor feeding at least a portion of said hot component back to saidcombustion chamber.

2. A system according to claim 1 wherein said combustion chamberincludes means forming a fuel input, and means for mixing said feed backportion with fuel at the input to said combustion chamber.

3. A furnace system comprising a combustion chamber including meansforming a fuel input, means for supplying a combustion gas to saidchamber, means forming an output path for combustion products from saidchamber, a vortex tube in said path for dividing the combustion productsinto relatively hot and cold components and means for feeding =at leasta portion of said hot component back to the input of said combustionchamber.

4. A system according to claim 3 including means for mixing said feedback portion with said combustion gas to preheat said gas prior to itsentrance into said chamber.

5. A system according to claim 4 wherein said vortex tube is of theuniflow type having hot and cold gas outlets at the same end of thetube.

6. A system according to claim 5 including means for maintaining acirculating heat transfer medium in heat xchange relation with the outersurface of said vortex tube and said hot component feed back means.

7. A system according to claim 6 wherein said heat exchange medium `iswater.

8. A furnace system comprising a combustion chamber, a blower forsupplying air to said chamber, a fuel inlet to said chamber, meansforming an output path for combustion products from said chamber, avortex tube in said path for dividing the combustion products intorelatively hot and cold components and a feed back line connecting theperiphery of said vortex tube with the input of said blower whereby thehot component of said combustion products is fed back to preheat the airpassing through said blower into said combustion chamber.

9. A system according to claim 8 wherein fuel is supplied to saidcombustion chamber through a venturi inserted between said blower andsaid chamber.

10. A furnace system according to claim 9 including means formaintaining a heat exchange fluid medium in contact with the outersurface of said vortex tube and the outer surface of said feed -backline.

11. A furnace system comprising a combustion chamber, means forming anair-fuel mixture `inlet to said chamber, means forming an output pathfor combustion products from said chamber, a vortex tube in said path-for dividing the combustion products into relatively hot and coldcomponents, means for feedin'g a portion of the combustion products fromsaid chamber through a return line to said mixture inlet, and means forfeeding back said hot component from the periphery of said vortex tubeto said return line.

12. A system according to claim ll wherein said return line includes anozzle capable of passing uids at supersonic velocities and said hotcomponent enters said return line at the output 'of said nozzle.

13. A system according to claim 12 wherein said nozzle feeds a difuserwherein said hot components are compressed above the pressure in saidcombustion chamber.

14. A system according to claim 13 including means for maintaining aheat exchange fluid medium in constaet with the outer surface of saidvortex tube and said hot component feed 'back means.

References Cited in the file of this patent UNITED STATES PATENTS %4,031Leahy July 12, 1910 1,719,684 Besta July 2, 1929 l,753,432 Isom Apr. 8,1930 1,837,7l3 Jacobus Dec. 22, 1931 1,952,28l Ranque Mar. 27, 1934FOREIGN PATENTS 1,1l9,245 France Apr. 3, 1956

1. A FURNACE SYSTEM COMPRISING A CUMBUSTION CHAMBER, MEANS FOR SUPPLYINGFUEL TO SAID CHAMBER, MEANS FORMING AN OUTPUT PATH FOR COMBUSTIONPRODUCTS FROM SAID CHAMBER, MEANS IN SAID PATH FOR DRIVING THECOMBUSTION PRODUCTS INTO RELATIVELY HOT AND COLD COMPONENTS AND MEANSFOR FEEDING AT LEAST A PORTION OF SAID HOT COMPONENT BACK TO SAIDCOMBUSTION CHAMBER.